The long-term goal of this research is to provide a complete molecular description of acetylcholine receptor function including ligand binding, ion permeability control and ion permeation. A specific approach used here is to characterize lipid and protein interactions important in the coupling of ligand binding to ion permeability. The electron spin resonance technique of spin labeling is being used to measure the lipid dynamics and lipid-protein association in membrane vesicles purified from the electric organ of the electric ray Torpedo californica. The effects of free fatty acids and local anesthetics on ion flux, ligand binding and spectral properties are being correlated. In addition, parallel studies are being carried out on reconstituted membranes prepared from purified acetylcholine receptor protein and defined phospholipids.